<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <style type="text/css">
    </style>
</head>
<body>
<input type="text" id="input" class="my brother" value="hello">
<div>
    <textarea name="" id="textarea" cols="30" rows="10">你好陌生人</textarea>
</div>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js">
</script>
<script type="text/javascript">
    $(function(){
        //jquery添加元素


        var c = $("#input");
        var txt3=document.createElement("p");
        txt3.innerHTML="文本-3。";
        c.after(txt3);
        var txt1="<p>文本-1。</p>";
        c.before(txt1);

        var txt2=$("<p></p>").text("文本-2。");
        $("div").append(txt2);
    });

</script>
</body>

</html>